An RFID (Radio Frequency IDentification) system, which has become popular in recent years, is used for article management, such as inventory management using RF tags attached to respective management target articles. In such an RFID system, RF tags are attached to respective management target articles, and the management target articles are managed in the following manner. That is, when the tag information of the RF tags can be read, it is determined that the management target articles are present, while when the tag information cannot be read, it is determined that the management target articles are not present. However, such an application of the RFID system has the following problems.
Firstly, there is a problem of unauthorized reading of tag information of RF tags. For example, in the case of using RF tags to manage commodities on store shelves in a retail store, a sales clerk who manages the commodities and consumers who plan to purchase the commodities can read the tag information of the RF tags which are attached to the respective commodities by a third party. In this case, for example, information on a commodity that is to be purchased or has already been purchased by a consumer can be linked to the consumer, which leads to a problem of invasion of privacy. Further, when raw materials stored in warehouses and products to be shipped are managed by the RFID system, a third party can read tag information of RF tags, which are respectively attached to the raw materials and products, so that the storage/delivery status of the raw materials and products can be disclosed to the third party. This poses an information security problem.
Secondly, there is a problem that the RF tags are costly. Currently, the cost of a UHF band tag has been reduced to less than about 10 yen. However, this cost is about two orders higher than the cost of a barcode that is used for article management, especially, commodity management. As a result, it is difficult in terms of cost to attach RF tags to respective articles for which the price is about 1000 yen or less.
A technique to solve such problems is disclosed in Patent Literature 1 to 5. Patent Literature 1 to 5 disclose a technique for managing articles in the same manner as in the method in which the RFID system is used. Specifically, Patent Literature 1 to 5 relate to a technique in which RF tags are provided on a shelf to monitor the presence or absence of an article on the shelf.
In Patent Literature 1 to 5, RF tags are arranged on a shelf. Articles are arranged such that each article to be managed (hereinafter referred to as “management target article”) prevents an RFID reader from reading a plurality of RF tags arranged on the shelf. Specifically, in Patent Literature 1 and 2, the management target articles are arranged between the RF tags and an antenna attached to the RFID reader, and the management target articles arranged between the RFID reader and the shelf prevent the reading operation of the RFID reader. On the other hand, in Patent Literature 3 to 5, each RF tag and the RFID reader are arranged on the shelf side, and interference portions provided on the respective management target articles are moved closer to the RF tags, thereby interfering with the reading operation of the RFID reader. It is based on the premise that the articles that can be managed or the interference portions contain metal, water, or the like, which prevents transmission of energy at radio frequencies.
According to the above-mentioned techniques disclosed in Patent Literature 1 to 5, the RF tags are not attached to the respective management target articles and are left on the shelf. This avoids problems such as information security problems and invasion of privacy problems due to unauthorized reading of the tag information of the RF tags attached to the respective management target articles. According to the techniques disclosed in Patent Literature 1 to 5, the first problem due to unauthorized reading of the tag information of the RF tags by a third party does not occur. Further, according to the techniques disclosed in Patent Literature 1 to 5, the RF tags are not attached to the respective articles and are left on the shelf. Therefore, each RF tag can be repeatedly used, and thus the tag cost per article is substantially equal to a value obtained by dividing the price of a tag by the number of times the tag is used. That is, according to the techniques disclosed in Patent Literature 1 to 5, the second problem that the RF tags are costly can be solved by using the RF tags a sufficient number of times.